A simple arithmetic of life is this: if cells in a tissue divide more frequently than they die, the tissue grows; if cells die more frequently than they divide, the tissue shrinks. This basic principle is enshrined as a ?hallmark? of cancer?for a cancer to exist it must evade cell death mechanisms that would shift this equation to attrition. For three decades my laboratory has worked to understand the core pathways of regulated cell death and how they are controlled at the molecular level. This program of research, the continuation of which is proposed in this application, explores the processes of regulated cell death in the forms of apoptosis and necroptosis, and seeks to understand how they are tied to other cellular physiologies, as they must be. Three general goals of this research are outlined as questions, as follows. A. What are the mechanisms of cell survival in apoptosis/necroptosis and how do these integrate with cell life? Here we use the concept of ?persisters,? cells that survive the activation of core apoptotic or necroptotic pathways, to probe the pathways that, when engaged, restrict these core pathways to enable transient resistance to the stimulus. We prioritize our ?hits? based on those whose expression correlates with patient outcome in cancer databases, including the TCGA and St. Jude Pediatric Genome Project. These are tested in cancer xenograft models. B. How do diverse processes of cellular life integrate with the core mechanisms of apoptosis? The mitochondrial pathway of apoptosis is generally known to depend on the activation of the Bcl-2 family effectors, Bax and Bak by BH3- only proteins. We will continue to explore alternative mechanisms of mitochondrial permeabilization and how they are regulated by components of the cellular physiology. Prioritization and testing is as above. C. How do diverse processes of cellular life integrate with the mechanisms of necroptosis? Necroptosis is a form of regulated necrosis that is actively inhibited by the action of a caspase, normally associated with apoptosis (but here with cell survival). We will continue our studies into the activation and regulation of necroptosis in relation to cellular physiology and develop tools to probe its activation in the context of cancer and other pathologies. While the understanding of the core pathways of cell death have led to one approved cancer therapeutic, our continued ?life and death? efforts set the stage for future success in this critical arena.